Carbon dioxide discharge system



April 3, 1945. c. H. LINDSAY CARBON DIXIDE DISCHARGE SYSTEM Filed July16, 1942 Patented Api.3, 1945 i CARBON DlOXlDE DISCHARGE SYSTEM CharlesH. Lindsay, Elmira, N. TY., assignor to American-La France-FoamiteCorporation, Elmira, N. Y., a corporation of New York y Application July16, 1942, Serial No. 451,129

8 Claims. (Cl. 62-1) The invention relates to aircraft fuel systems andmore particularly to'fsystems for delivering carbon dioxide gas intoaircraft fuel tanks for the purpose of avoiding development of ignitiblevapors in the space above the liquid fuel therein. Ordinary carbondioxide discharging systems applied to this purpose have the objectionthat they do not function reliably because they store' the dioxide inthe highly compressed liquid form, and,

when discharging through the fine orifice necessary to give the requiredslow rate are subject to stoppage from the freezing of any water withwhich the dioxide may be contaminated or which may find its way into thesystem. It is dlicult to obtain carbon dioxide entirely free frommoisture, also to keep moisture from condensing within the tubing of thesystem, and even less than 1% can defeat a proper discharge for thepurpose indicated, by clogging the fine nozzle orifice with Water ice.This may occur either from ice as fine particles frozen while suspendedin the flowing dioxide, or as vapor, or as an ice film freezing on theinside of, and thereby closing the nozzle tip. The freezing temperatureoccurs from the rapid expansion of the dioxide as its pressure isrelieved 'and as it changes from liquid to vapor form. lThe temperaturedrop is most pronounced at the nozzle tip, but water-freezingtemperature can arise at any point along the line from the tip back tothe storage flask during the discharge. It is of great importance thatthe discharge when started shall be complete and uninterruptedthroughout the required period. These systems are put in use just beforeengaging in combat and their failure might mean disaster.

This invention is a liquid dioxide discharge system rendered free of alldanger of ice-clogging. by virtue of a special construction andorganization of the discharge passage which forestalls the movementoflwater, whether, in vapor, liquid, or

solid form, so far through the discharge lineas to reach the cold nozzletip. As above indicated, the water may be present in liquid or vaporform, and it may also be in solution in the liquid dioxide. This latterfact, as well as theefact that the specic gravities of water and liquiddioxide.

are normally not very dierent, may account for the failure oftheordinary precautions, such as short dip-tubes, to prevent dischargeofthe way ter, in addition to which note must be taken of the ebullientcondition of the liquid dioxide which begins on the instant of anyrelease of pressure, as on discharge, so that if the water could beassumed to have collected as a pool in the bottom of the 'iiask theinternal ebullient commotion would of course tend to scatter itthroughout the mass of the dioxide, thus encouraging its entry into thedischarge line. Proceeding on the theory that the Water and liquiddioxide are not susceptible of sharp separation for the reasonmentioned, the discharge passage of this invention includes thecombination of two different types of water-restraining agencies, oneinvolv'- lng av labyrinthic entrance to the discharge line and the othera refrigerated eliminator at the other end, so that moisture in any ofits forms is precluded from reaching the tip. This com@ blnation hasbeen found consistently safe in operation and has been accepted as such,giving reliable discharges even in cases where water has been purposelyadded to the dioxide for test pur- -poses in amounts as high as 1.5% byweight and which of course is far greater than would be experienced inpractice.

AThe accompanying drawing shows the preferred form of the new dischargepassage, Fig. 1 being a diagrammatic section of the system, Fig. 2 anenlarged section of the labyrinthic receiving end of the passage, Fig. 3an axial section of the 1,921,411, which is Well known to those skilledin .Y

and also to avoid excessive pressure within the nozzle and Fig. 4 amodified form of the waterdrainage provision.

The"liquid dioxide container or flask and its operating head l will berecognized as conven tional and will be understood to confine the liquidunder a pressure in the neighborhood of 850 lbs. at normal temperatures.An example of such operating heads will be found in Patent No.

this art. On opening the operating head, as by perforating the sealingdisc therein as customary, liquid dioxide ows upwardly through the diptube structure 2 and thence through the piping v3 to the nozzle 4 in thefuel tank 5 to be protected. It will be understood that the dischargepassage starts at the foot or entrance to the dip tube structure andends at the nozzle orifice,

which is of smaller size than customary in dioxide systems, being in heorder of from .025 inch to .040 inch diameter. Such ne holes arerequired in order to prolong the discharge period gardless of variationin the lengths of different flasks with which it may be used, therebyinsuring a maximum liquid evacuation of the flask when discharged, andat the `same time steadying the structure against vibration,

The lower telescopic section 6 contains or constitutes the labyrinthicreceiving entrance above referred to. It comprises an inner insertedcylindrical member or tube 8 appropriately mounted therein to formtherewith an annular chamber or passage 9, which is shallow inproportion to its circumference and width. The entrance thereto is atits lowest point, provided by a ring of radial holes Ill andthe exittherefrom is by radial outlet holes II at its top leading into theinterior of the inserted member 8. Liquid dioxide enters the lower holesby horizontal flow in the flask proper and then flows first upwardlythrough this shallow passage, thence inwardly through the radial holesII and thence upwardly again into the upper section 2 and onwardlythrough the piping 3 toward the nozzle. The cross sections of theannular chamber 9 and of its entrance and exit holes are substantiallyequal to the cross section of the tube 2, or at any rate equal to thatof the perforation made in the sealing disc so that the flow occurswithout any particular restriction or choking effect at this point. Theconstruction constitutes a water-restraining means, functioningapparently by the impingement of the liquid on the surfaces of theshallow passage, which holds thewater or some of it back, by causing itto adhere to such surfaces. After the discharge is over the water soretained can be found, usually then frozen,. in the labyrinthic passage.

From thiswaterjrestraining means the dioxide Y good conductor of heatand preferably in tubular form. One end of` this screen is attached (atI3) around the interior neck of the nozzle tip I4 and preferably by'soldering it thereto so as to establish a good thermal connectiontherewith. The tubular screen is of extended length, many times its owndiameter, and being closed at its freev end all of the dioxide must passthrough it in order to reach the nozzle.v

At the time of discharge the nozzle tip instant-l ly acquires a sub-zerotemperature as the effect of the abrupt expansion through its orice, andthe soldered connection transmits this low temperature to the screen sothat water. even in so ne a state as to be'regarded as dissolved in thedioxide, encountering this cold metal mesh is promptly frozen thereonand therefore does not reach thetip. At the same time such particles ofwater or water vapor as may have become frozen in the piping beforereaching the screen are also .caught by it and thereby kept fromplugging thetip. The screen thus lserves as amoisture eliminator both byits refrigerating action on dissolved or liquid water and by itslmechanical screening action. In the latter respect of continuoudischargeduring the effective discharge period and notwithstanding the fine sizeof the discharge outlet with which these systems must be provided.

I have found that the refrigerated screen tends to collect less frostwhen the dioxide entranceinto the dip tube or into a shallow chambertherein, such'as the chamber 9. is by horizontal flow as through theradial holes I0, rather than by way of a dip tube that is open-ended atits foot, indicating that such direction of entering is a factor in theresult, and also that it is still further reduced .by locating a flangeIl immediately below such radial holes, and I accordingly prefer thisconstruction of the receiving entrance.

Since it is obviously desirable that no water should remain over in theask when recharged with dioxide, provision for the` removal of any suchwater is provided by forming the inner or impingement member 8 of thedip tube with a tubular extension I6 closed at its end and constitutingthe very 'foot of the dip tube, pressed against the ask bottom by thetelescope spring as above pointed out. This extension is in line withthe axis of the dip-tube and provided with a lateral port normallyclosed by a ball valve I1 and spring I8. By inserting a proper suctiontube through the flask head and pushing it into this extension, the ballI1 can be unseated, letting any water in the flask bottom iiow into theextension, so that it can be sucked up by the tube, thus removing anyresiduum of water in the flask before recharging it with dioxide. Thisis much easier than unscrewing the discharge head to drain out water.

An alternate method of water-drainage, as indicated by Fig. 4, may insome cases represent the preferred form, as for instance where thedip-tube is curved or otherwise obstructed against the use of a suctiontube. Insuch cases this same water drainage valve can be located at orin the head itself, as indicated at I9 inthis figure. When such valve ispressed open by a suitable tool introduced through the opened head, the

flask being inverted, any water can be drained 'closedat both its endsand provided with lateral hpies near its lower end to receive dioxideand lateralvholes near its upper end through which dioxide passes in itscourse toward ysaid nozzle, the cross area of said shallow chamber andthe aggregate areas of said holes being not substantially less than'that' of the discharge passage elsewhere.

2. A carbon dioxide discharge system comprising a flask of liquiddioxide having a discharge passage comprising a dip-tube within theflask connected to a discharge nozzle through which such liquid expandsto vapor. phase and means for retarding the passage of water in thedioxide to said nozzle comprising said dip-tube closed at its lower end,aradially projecting flange on said closed end and lateral dioxideentrance holes leading into such tube just above said flange.

' 3. A carbon dioxide system comprising a flask of liquid dioxide havinga discharge passage inV cluding. an interior tubularv conduit and meansfor y l 9,873,087 removing any water retained in the yflask comprising avalve port in said conduit, a valve normally closing such port, saidvalve being operable mentl introduced through said dip-tube and` adaptedto allow water'in the flask to enter said dip-tube below the holestherein.

5. A carbon dioxide system comprising a ask oi liquid dioxide having adischarge head iormed with a tubular part projecting into the ask, aport in such part and a valve for said port located to be openable by aninstrument inserted through the discharge head, whereby water collectingin said flask can be drained out through said head.

6. A carbon dioxide system for slow discharge into a lfuel tankcomprising a ask of liqueed carbon dioxide having a discharge passagecomprising a tube within the flask and piping connecting such tube to anozzle within said tank, said tube having its only entrance organized inthe form of labyrinthically related holes and located in the lower partof the ask to cause said passage to conduct only liquid dioxide duringthe effective part of the discharge period, such entrance holes being ofsuch area as to offer. no greater resistance to iiow than any other partof such discharge passage and said nozzle having a i'lne orifice suitedfor discharging into a fuel I l l l 7. carbon dioxide discharge systemf/or slow discharge into a fuel tan comprising a nozzle inA said tank, aflask of liquid dioxide having a discharge passage including a. tubewithin the flask organized to receive only liquid therefrom during theeffective part of the discharge period and piping connecting such tubeto the nozzle in the tank having a restricted oriice through which theliquid dioxideexpands to vapor phase, said orifice constituting thepoint of maximum restriction to the outflowof the liquid dioxide andsaid passage including a water-restraining means associated with the'foot of said interior tube in the flask and a second kwater-restrainingmeans constituting part of said nozzle capable of \re taining watervaporv closely associated with said orifice in the'nozzle, and means atthe head of the flask normally coniining the liquid dioxide thereinadapted 'to be opened to permit immediate unrestricted flow through saiddischarge passage.

8. A carbon dioxide system for slow discharge t into a fuel tankcomprising a'nozzle in said tank,

a ask of liquefied carbon dioxide having a dl's.

charge passage comprising a tube within the iiask and piping connectingsuch tube to a nozzle within said tank, said tube being closed-ended andhaving its only entrance organized in the form of holes in the side wallof said tube located in the lower part of the flask to cause saidpassage to receive only liquid from the ask during the ef fective partof the discharge period, such entrance holes being of such area as tooer no greater resistance to flow than' any other part of `suchdischarge passage and said nozzle having a fine oriiicesulted for slowlydischarging into.

a fuel tank and containing a fine screen partaking of the subzerotemperature at said 4orifice and intercepting the flow thereto, saidscreen having suiiicient area to freeze and retain thereon any waterencountering it without itself becoming a stoppage to flow.

:CHS H. LINDSAY.

